Closed breech rocket gun



Dec. 5, 1967 5. R. KRUZELL CLOSED BREECH ROCKET GUN 2 Sheets-Sheet 1 Filed Oct. 14, 1965 I N VEN TOR 650165 ,6 KFUZELL in me F M a a wax fiwws Dec. 5, 1967 G. R. KRUZELL CLOSED BREECH ROCKET GUN MW l 2 w. m, w :I:

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Filed Oct. 14, 1965 5 3m 9. mm 5 United States Patent 3,355,989 CLOSED BREECH ROCKET GUN George R. Kruzell, 4301 Hotchkiss, Bay City, Mich. 48706 Filed on. 14, 1965, Ser. No. 495,964 7 Claims. (Cl. 89-187) ABSTRACT OF THE DISCLGSURE A closed breech rocket gun in which the firing pin is movably housed within a passage through the sliding bolt so as to be free for retraction or recoil after each firing, the firing pin having a piston slidably engaging the walls of said passage and utilizing the gas pressure for producing sealing engagement between a rearwardlypresented sealing face on the firing pin and a cooperating sealing face of the bolt.

This application is a continuation in part of my application Ser. No. 382,863, filed July 15, 1964, now U.S. Patent No. 3,227,045, granted Jan. 4, 1966 relating to improvements in a firearm of the type provided with a closed breech. In the type of firearm disclosed in the parent application, the firing pin is provided with a forwardly presented sealing surface in cooperative sealing engagement with a rearwardly presented sealing surface within the bolt, the bolt in turn being urged into sealing engagement with the rearwardly directed breech opening, whereby the bolt and the firing pin will jointly seal the rearwardly directed breech opening against the escape of the exploding gases in the firing chamber.

In such a firearm, the firing pin is normally urged rearwardly by its spring toward a retracted position and away from sealing relation with respect to the bolt and the breech opening. Thus, the forces arising from the gas pressure are transmitted jointly through the firing pin and the bolt to separate cam surfaces of the common locking and actuating member for both the firing pin and the bolt. Since the cam surface of said member which actuates the firing pin has a greater slope than does the cam surface of said member which engages the bolt, the transmission of such retraction forces through the firing pin to the said member will exert a proportionately greater retracting or withdrawing effect on the said member than will similar forces transmitted through the bolt.

Moreover, as regards the sealing relation between the firing pin and the bolt, the force provided by the aforesaid common locking and actuating means is opposed by both the spring and the gas pressure acting on the firing pin, both of which tend to unseat and, therefore, to reduce the efficiency of the seal.

The present invention has been conceived with the foregoing consideration in mind, and relates to improvements through which it has been found possible to utilize the forces arising from pressures of the gases for increasing the sealing pressure between the bolt and the firing pin and thus the effectiveness of their seal; to utilize the force of the firing pin spring for augmenting such sealing pressure; and to prevent the transmission of retraction forces through the firing pin to the said common locking and actuating member.

These ends are obtained in the present invention by providing the firing pin with a rearwardly directed sealing surface for cooperation with a forwardly presented sealing surface of the bolt, as Well as by providing the firing pin with a piston disposed for movement in a pressure chamber or cylinder within the bolt, into which the exploding gases are admitted to exert a rearward sealing pressure on the piston. The sealing surface or area of 3,355,989 Patented Dec. 5, 1967 the firing pin may thus advantageously comprise a rearwardly presented surface or area of the piston.

In the improved construction, the said common actuating member is relieved of its locking function with respect to the firing pin, though its function in locking the bolt is maintained. To this end, the actuating force of the said member is transmitted to the firing pin through a striker, which is normally retracted from the firing pin, to permit free rearward movement thereof. The recoil force on the bolt, therefore, is transmitted to the said member solely through the bolt by way of its more favorably inclined cam surface. Thus, the total retraction forces imposed on the said member are reduced as compared to the structure disclosed in the parent application, permitting the use of a lighter or weaker projection spring for the said member and resulting in a firing mechanism generally requiring less force for its operation.

Nevertheless, the said locking path and actuating member, by projecting across the aligned paths of retraction of both the firing pin and its striker (as well as of the bolt) affords protection against accidental rearward displacement of either the striker or the firing pin or of the various components or fragments thereof.

In this application there is shown and described only the preferred embodiment of the invention together with minor modifications of certain of its details, and specific language is used in describing same. However, it will be understood that the drawings and description are merely by way of exemplification rather than limitation of the invention.

In the accompanying drawings:

FIGURE 1 is a vertical medial section through the firing mechanism of a shoulder type firearm embodying the invention, with parts in the operative positions which they assume in firing a round of ammunition.

FIGURES 2 and 3 are sections on the lines 2-2 and 3-3 respectively of FIGURE 1.

FIGURE 4 is an enlarged section, taken in the same plane as FIGURE 1, through the receiver and the adjacent portion of the gun barrel.

FIGURE 5 is a fragmentary view generally similar to FIGURE 4, but with the bolt retracted, and with a fresh round of ammunition positioned in the receiver for delivery into the firing chamber by the return or projection movement of the bolt.

Referring now in detail to the preferred embodiment of the invention, as specifically illustrated in the accompanying drawings:

The firearm there illustrated comprises a generally conventional gun barrel 10 formed with a bore 11 therethrough which defines a firing chamber 12 at its rear end and terminates rearwardly in a breech opening defined by a rearwardly presented conical sealing surface 13. The bore 11 may, if desired, be rifled in conventional manner (not shown) for imparting spinning stabilizing movement to a projectile p of a round of ammunition R loaded into the firing chamber through the breech opening 13. The round of ammunition here illustrated also includes a propellant charge of explosive c which may consist of conventional gun powder in which the grains are bonded together by a suitable adhesive and also are adhesively or otherwise secured to the projectile p. It is contemplated that the charge c will have sufiicient strength and shape maintaining qualities as to permit elimination of the usual metal cartridge or shell casing. By eliminating the shell casing or cartridge, with its associated expense, it is also possible to eliminate from the gun structure the usual means or mechanisms for extracting and ejecting the casings or expended cartridges after firing, though such mechanism or means may, if desired, be included, as hereinafter more specifically described.

The rounds of ammunition R may also represent rocket type or reaction missiles, in which event the barrel may be provided with suitable pressure release ports and passages, in accordance with known practice, as exemplified in US. Patents Nos. 2,802,399 and 2,515,180.

Means defining the breech opening 13 are exemplified by the bushing 15 functioning in effect as a rearward extension or portion of the barrel, but in the present instance formed of a somewhat softer metal such as bronze whereby to effect an improved and substantially conforming sealing engagement with the bolt 16. A hollow receiver 17 is rigidly connected to the barrel with its interior bolt well 18 aligned with the bore 11. In the present embodiment the forwardly opening end of the receiver 17 snugly receives and is shrink fitted, threaded on or otherwise suitably secured to the barrel. With this arrangement, the bushing 15 at the rear end of the barrel also is housed within the receiver.

The weapon of the preferred embodiment is of a sufficiently small size that it may be employed as a shoulder gun, and for this purpose it includes a supporting stock 20 having at its forward end an adapter piece 21 received within and closing the rear end of the receiver as at 22 and so firmly secured therein as by the attaching means or cross pin 23. If desired, the stock may be firmly anchored to the adapter 21 by means of the reinforcing rod 24 extending lengthwise through the stock and having its forward end 25 threaded into a bore within the adapter.

The bolt 16, which exemplifies the breech closing mechanism of the present embodiment, is guided in the bolt well 18 of the receiver for movement in alignment with the bore 11 and its breech opening 13. Preferably the bolt 16 is of a generally cylindrical cross sectional shape proportioned and arranged for free sliding movement within the bolt well 18 between its rearwardly retracted position, as shown in FIGURE 5 and its forwardly projected position, as shown in full lines in FIGURES 1 and 4. At its forwardly directed end, the bolt 16 is provided with a reduced diameter tapered nose 27 defining a generally forwardly converging sealing surface for operative flush sealing engagement with the sealing surface 13 around the breech opening. Preferably the sealing surfaces 13 and 27 are conically tapered in a forwardly converging manner and at identical angles, whereby to achieve efficient sealing action over a wide area of engagement.

For urging the bolt 16 from its retracted position toward its projected operative sealing position there is provided a usual bolt return spring 30, here exemplified as a coil spring axially compressed between the bolt operating handle 31 and the blind end of a bore 32 in the receiver within which one end of the spring is guided and housed. The other end of the spring may be supported on and located by a guide pin 33 affixed to the bolt handle 31. The bolt handle will be seen to project externally of the receiver through a longitudinal slot 34 so that its external end may be grasped and pulled rearwardly to manually retract the bolt 16 to substantially the position shown in FIGURE 5.

For releasably retaining or latching the bolt in this retracted position, there is provided a sear 35 which is guided for movement into and from engagement with the bolt through an opening 36 in the receiver. The inner end of the sear 35 is formed to present an inclined cam surface 37 presented for operative engagement by the bolt during its retraction movement to automatically urge the sear transversely outwardly through its guide opening 36 and thus out of obstruction relation with respect to the rearwardly moving bolt.

The bolt is formed with a forwardly presented locking face 38 for holding or cocking engagement by the sear incident to retraction of the bolt. By abutting engagement with the forwardly presented locking face 38 of the bolt, the sear will then releasably latch the bolt in its retracted and cocked position. Selective disengagement of the sear 35 from the bolt for firing of the weapon, is under the control of a conventional trigger 40, pivoted at 41 to the receiver and having a depending lever arm 42 operatively connected to the sear 35 through the pin and slot connection 43. The trigger 40 is normally urged to its inoperative position by means of a conventional coil spring 44 (shown in FIGURE 1), under compression between the trigger 40 and the receiver. It will be apparent that the spring 44 also acts through the trigger and its connection to the sear 35 to resiliently urge the latter into the bolt well 18 for operative latching engagement with the bolt.

The structure as heretofore described is similar to that disclosed in the earlier parent application and constitutes a part of the present invention only insofar as it is combined and coacts with the improvements hereinafter disclosed in the bolt and firing pin construction and operation.

The bolt 16 is formed with a passage or bore 45 extending completely therethrough for housing and guiding the firing pin 46 and its related components. The said passage is defined in the present embodiment by an axially disposed cylindrical bore 45 having portions 45a and 4512 respectively disposed on opposed sides on an annular shoulder 78 through the relatively reduced diameter central opening of which is slidably guided, the rearwardly extending extension or anvil portion 46a of the firing pin 46. The firing pin is supported near the forward end of the bolt for movement in alignment with the firing pin striker 48 which is housed in the rearwardly disposed portion of the bore 45 and is provided with a reduced diameter forward end 48a for impacting engagement with the relatively aligned rearwardly directed end of the firing pin anvil 46a to project the firing pin forwardly so that its reduced diameter forward end portion 47 may be projected sharply forwardly by the striker impact to engage the ammunition primer I of a round of ammunition R in the firing chamber in the rear end of the barrel 10.

Preferably the forward reduced diameter operative end 47 of the firing pin is slidably guided through a centrally apertured bearing member 79 exemplified by a metal plug threaded into the forwardly opening end of the cylindrical bore.

The rearwardly disposed bore portion which guides and accommodates the firing pin striker 48 opens rearwardly through the rearwardly directed sloping cam surface 61 of the bolt. The main body portion of the striker 48 is preferably cylindrical and proportioned for freely sliding reception and guidance in the bore portion.

Normally before firing, and with the bolt in retracted, cocked position, the striker is resiliently rearwardly retracted so that its inclined rearwardly directed cam face or surface 60 projects rearwardly out of the bore and beyond the surrounding cam surface 61 of the bolt for operative engagement by the member 57, while the forwardly directed reduced diameter operative or impacting end 48a of the striker similarly is retracted rearwardly away from the firing pin to gather momentum for its impacting engagement with the firing pin. Such retraction of the striker is produced by means of a coil spring 53 disposed around the reduced diameter forward end of the striker and under compression between the shoulder 89 at the junction of the said reduced diameter portion and main body of the striker and an annular collar 83 which is fixed within the bore by means of a set screw. The extent of rearward retraction of the striker under the infiuence of the spring 53 is limited by any conventional means, such as the set screw 84 threaded radially through the bolt and into its bore 45 for sliding reception of its free inner end in a slot 85 in the main body of the striker.

For effectively sealing the through passage 45 in the bolt defined by the interconnected bore portions thereof, the firing pin is provided with a piston 86 of relatively enlarged diameter adjacent its forward end. Piston 86 is snugly received and guided within the pressure chamber or cylinder defined by the forward portion of the bore 45 to be acted upOn by the exploding gases in a manner to urge the firing pin rearwardly. Also, the firing pin is provided with a rearwardly directed sealing surface 49 preferably defined by a rearwardly converging conically tapered portion of the piston 86 and arranged for sealing engagement with a similarly tapered interior conical sealing surface 50 preferably defined by a bushing of bronze or other soft metal having a suitably tapered bore therethrough to define the sealing surface and having a cylindrical exterior proportioned for a snug reception in the cylinder.

The firing pin is normally urged to retracted position by means of a coil spring 75 which encircles it Within the bore 45 and is under compression between the annular shoulder 78 and a radial enlargement or projection 87 on the firing pin, as exemplified by a collar fixedly secured on the firing pin by means of a set screw.

Except during its actual forward projection and retraction movement for firing purposes, the firing pin is normally urged rearwardly by its spring 75 to seat its sealing surface 49 against the mating surface 50 of the bolt. The spring pressure is thus advantageously employed to augment the seating force which will be exerted on the firing pin through pressure of the exploding gases in the firing chamber and barrel.

Where the reduced diameter operative end portion 47 of the firing pin is guided through a bearing 79 at the forward end of the pressure chamber 45a as in the instant case, the bearing is preferably provided with one or more ports 88 for the admission of gases into the forward end of the chamber for actuation of the piston.

Thus, with the preferred arrangement of the firing pin 46 here illustrated, the pressure of exploding gases created by firing the gun will enhance the sealing engagement between the sealing surfaces 49 and 50 of the firing pin and the bolt. Therefore the integrity of the seal thus provided will be increased by the gas pressure. In addition, the sealing pressure will be augmented by the action of the firing pin retraction spring 75, as contrasted to the structure disclosed in the parent application in which both the gas pressure and the thrust of the firing pin spring tend to decrease the sealing pressure.

Also, it will be apparent that when the bolt locking member 57 is released and projected to actuate the firing pin striker, the member 57 will engage the striker 48 only during the initial portion of the movement of the latter. The final movement of the striker 48 occurs through momentum arising from its initial movement, and after the trailing end cam surface 60 of the striker is disengaged from the bolt lock 57 by movement into the rear end of the bore 45. Immediately following its impact with the firing pin anvil 46a, the striker is retracted by its spring into abutting engagement with the bolt lock 57, in which position it is disengaged from the firing pin and incapable of transmitting recoil forces to the member 57. Thus the entire recoil force on the bolt 16 arising from firing of the gun is transmitted through the more gently sloping cam surface 61 of striker 48 and will obviously result in exerting a proportionately smaller component of retraction force on the bolt lock than would be the case as to recoil forces transmitted to the member 57 through the relatively more sloping cam surface 60.

The mechanism for locking the bolt 16 during firing, as well as for actuating the firing pin striker 48 to drive the firing pin 46 forward into its projected position, includes a locking and actuating member 57 common to and cooperating with both elements 16 and 48. It follows that the member 57 and the striker 48 constitute parts of a firing pin actuating means. The member 57 is guided in a bearing sleeve 58 for linear movement into and from the receiver transversely to and across the paths of movement of the striker 48 for the firing pin 46 and of the bolt 16 to engage behind rearwardly presented portions 60 and 61 respectively of these members whereby to prevent their retraction movement. A set screw 59 as shown in FIGURES 4 and 5, limits the projection movement of the member 57, the inner end of the set screw being received in a slot in member 57 as shown. The locking and actuating member 57 is constantly urged inwardly into operative engagement with the bolt 16 and firing pin striker 48 by means of its actuating spring 62 which is compressed between the member 57 and a suitable spring seat 6-9 at the lower end of bearing sleeve 58-. It will be understood that the bearing sleeve is suitably fixed to and functions as a stationary part of the receiver 17.

The rearwardly presented portion of the firing pin striker 48, exemplified by the inclined or sloping cam surface 60, is adapted for cammiug engagement by the upwardly projected member 57. The slope of the cam surface 60 is sufiicient to produce rapid projection of the firing pin striker 48 into impacting engagement with the firing pin 46, so as to drive the latter into detonating engagement with the primer or ignitor I of an ammunition round within the firing chamber 12, and thus is normally greater than that of the cam surfaces 61 and 63.

Because of the location of the firing pin striker 48 within and surrounded by the bolt, it will be apparent that before the member 57 can engage and commence the actuation of the striker 48 and its associated firing pin, it will have had to extend at least partially across the path of rearward retraction movement of the bolt to obstruct or block such movement. After the locking and actuating member 57 has advanced far enough to project the striker and firing pin forwardly into firing position, it will also be disposed in obstructing and blocking or locking relation rearwardly of the firing pin striker to prevent retraction thereof.

Inclined cam face or surface 61 of the bolt is adapted for coaction with the similarly inclined cam surface 63 of the member 57. This one surface 63 in the present embodiment, is relied upon both for its camming function with respect to the bolt as Well as for locking engagement with the bolt.

It will be seen that the portions 60 and 61 of the firing pin striker 48 and of the bolt respectively, together with the inclined surface 63 of the locking and actuating member 57, exemplify cooperating cam means on the several such elements for successively urging and locking the bolt against retraction from its projected position, and for then operatively projecting or actuating the firing pin striker 48. In addition, the cam surface 63 serves to augment the action of the bolt spring 30 in firmly urging the bolt toward its fully seated position in sealing engagement with the sealing surface 13 which defines the breech opening. In the event the forward projection of the bolt is arrested before the latter is substantially in fully projected breech closing position, the bolt in turn will arrest the upward projection movement of the member 57 before the latter can actuate the firing pin striker 46. Similarly, in the event of malfunctioning or failure of the member 57 or its spring 62, the firing pin will not be actuated and the weapon will thus not be fired.

In order to permit retraction of the bolt 16 for loading or reloading of the weapon it is necessary to retract the member 57 from its locking position. Where the gun is to be employed as a single shot weapon, the locking and actuating member 57 may be manually retracted by suitable actuation of its release rod 64, hereinafter more fully described.

In order that the locking and actuating member 57 may not arrest or unduly obstruct the projection movement of the bolt 16 as same travels from its retracted and cocked position shown in FIGURE 5, to its forwardly projected breech closing position shown in full lines in FIGURES 1 and 4, the locking and actuating member is provided with a rearwardly and upwardly presented gently inclined cam surface 67 for camming engagement with the forwardly presented tapered nose 27 of the bolt. The

engagement between these two cam surfaces obviously effects retraction of the member 57 to an inoperative and nonobstructing position at one side of the bolt, incident to the forward movement of the latter past member 57.

The release rod 64 for member 58 is provided at its rear end with a cam face 65 for operative engagement with a cam face 66 on the member 57, to retract same. Thus rearward movement of the rod 64 through its slide bearings 66 and 67, retracts or disengages the locking and actuating member from the firing pin and bolt.

It will be apparent that the structure as described up to this point will sufiice for operation of the gun as a single shot weapon. To cock the gun, it is necessary first to manually retract the locking and actuating member 57 in any suitable manner, for instance by manually actuating its release rod 64, while the bolt 16 is retracted and cocked by manual actuation of its handle 31. Single rounds of ammunition may be manually inserted into the receiver 17 through its loading port 68 to thereafter be moved into the firing chamber and fired by actuation of the trigger 40 which disengages the sear 35 from the bolt, with ensuing forward projection of the bolt.

An important aspect of the invention consists in its adaptation for either fully automatic or semi-automatic firing, by the addition thereto of a conventional ammunition magazine 70, together with means shown in FIGURE 1, exemplified by the gas cylinder and piston unit 71 operatively connected to the locking member 57 through a suitable linkagage, preferably including release rod 64, to automatically retract or disengage the member 57 from both the bolt and the firing pin striker 16 and 48 respectively, in properly timed relation to the firing of each round of ammunition. The timing is such as to permit automatic retraction of the bolt 16 by residual gas pressure Within the barrel 11 and the automatic loading or delivery of a fresh round of ammunition from the magazine 70 in advance of the bolt during each retraction thereof, in readiness for movement into the firing chamber and firing on the next ensuing forward projection of the bolt.

As above mentioned, the magazine 70 is of usual type adapted to contain a plurality of rounds R of ammunition (though but one such round is shown) and having a follower 72 urged upwardly by a spring 73 for conveying the rounds of ammunition successively upwardly into the receiver.

The gas cylinder and piston unit 71 has its cylinder in communication with the bore 11 of the barrel by means of a passage 74 appropriately located along the length of the barrel to admit gas to the cylinder just before the projectile P leaves the barrel, and at a time when the residual gas pressure within the bore will be ample to automatically retract the bolt 16, but insufficient to produce a dangerous rearward blast through the breech opening 13.

The piston 75 of the unit 71 normally is located within its cylinder rearwardly of the gas passage 74, to be forced rearwardly by the gases admitted into the cylinder. Its rearwardly projecting piston rod 76 is supported by the piston for endwise abutment with the release rod 64. The rearwardly presented end of the release rod 64 is adapted for projection into the bearing sleeve 58 through a suitable located opening so that its inclined cam surface 65 may coact with cam surface 66 of the member 57 to depress or retract the latter completely out of the path of the bolt 16. A spring 77 normally urges the release rod to its released position.

A plunger 80 guided through the housing of the piston and cylinder unit 71, may be manually thrust into endwise abutment with a projecting lug 81 on the release rod, to facilitate manual actuation of the latter, though this is not essential.

In the operation of the invention, where it is desired to fire the gun automatically, the gun is loaded and cocked, after placing a loaded magazine 70 in operative relation with respect to the loading port 68. Upon retraction of the bolt, the magazine spring 73 automatically feeds a round of ammunition into the receiver in the path of projection movement of the bolt 16. The trigger 40 may then be suitably actuated to disengage the retracted bolt, whereby same may move forwardly under the influence of its spring 30, ramming the round of ammunition into the firing chamber 12 and also thrusting the locking member 57 aside by the camming engagement between said member and its tapered nose 27.

The ensuing spring projection of the locking and actuating member 57 serves to cam the bolt forwardly into fully seated sealing position with respect to the breech opening 13 and actuates the firing pin 46 to fire the round. Just before the fired round leaves the barrel, pressurized gas from the rear of the projectile P is admitted to the gas piston and cylinder unit 71 through the passage 74, thereby actuating the said unit and its linkage means 76, 77 to automatically retract the member 57 to inoperative position. This permits automatic recoil or retraction of the bolt 16 by residual gas pressure within the barrel, to effect an automatic reloading from the magazine 70. In the event the trigger 40 is released immediately after firing a given round, the rearwardly projected bolt will be engaged by the sear 35 and held in cocked position to be released by a subsequent actuation of the trigger 40 for semiautomatic firing. However, fully automatic firing may be achieved simply by maintaining the sear 35 retracted to permit free reciprocation of the bolt and repeated automatic firing, either until the trigger is released or until the ammunition is exhausted from the magazine 70.

In the preferred embodiment of the invention, the locking and actuating member 57 is disclosed as having but a single cam face 63, for cooperation with both the firing pin striker 48 and the bolt 16, though it is not intended to preclude the provision thereon of separate cam surfaces with similar or relatively different slopes for coaction with the bolt and firing pin striker.

Because of the relatively greater slope of the cam surface 60 of the striker 48, it will be apparent that, if the member 57 were required to resist recoil forces transmitted from the firing pin through this striker cam surface 60, a larger component of such force would be exerted as a retracting force on the member 57 than is true in the instant invention, in which the striker is displaced rearwardly from the firing pin except at the instant of its impact therewith. Further such disconnection of the firing pin and its striker permits utilization of the entire recoil force on the firing pin for sealing it against the bolt. In addition, it is thus made possible to employ the piston and cylinder structure of the invention for applying a considerably greater recoil force directly on the firing pin, than could safely be done heretofore.

Although only the preferred embodiment of the invention is specifically disclosed herein, it is intended to cover all changes and modifications of such embodiment which do not constitute departures from the spirit and scope of the invention.

Having thus described my invention, I claim:

1. A firearm comprising a barrel formed with a bore therethrough defining a firing chamber at its rear end, and terminating rearwardly in a breech opening, a receiver operatively connected with said barrel, a bolt guided in the receiver for movement in a pre-determined path between rearwardly retracted and forwardly projected positions, selectively releasable means for retaining the bolt in its retracted position, and spring means for urging the bolt to its projected position, said bolt being formed with a passage therethrough in alignment with said barrel and said firing chamber and opening through the front and rear ends respectively of the bolt, and a firing pin slidably disposed in said passage for operative projection and retraction through the open forward end thereof, the improvement in accordance with which said bolt is formed with a forwardly directed annular sealing surface within said passage, said firing pin being provided with a rearwardly directed sealing surface in said passage for sealing engagement with the sealing surface of said bolt in the retracted position of the firing pin, a piston afiixed to said firing pin rearwardly of the forward end thereof and within said passage, a portion of said passage snugly slidably receiving said piston and defining therewith a variable volume chamber forwardly of the piston, said chamber communicating with said breech opening through the open forward end of said passage, and firing pin actuating means for projecting said firing pin forward-1y and immediately releasing same for rearward movement in response to the pressure of exploding gases in the firing chamber.

2. A firearm as defined in claim 1, including resilient means carried by said bolt and acting on the firing pin to retract same and to supplement the action of said gases in applying sealing pressure to the firing pin.

3. In a firearm as defined in claim 2, the further improvement wherein said firing pin actuating means comprises a firing pin striker guided in said passage rearwardly of the firing pin for forward projection into impacting engagement with the firing pin, said striker being fully received in said passage at the time of such engagement, and means resiliently urging said firing pin striker rearwardly to a pre-determined retracted position in which its rear end projects rearwardly from said passage and beyond the rear end of said bolt, a bolt lock member guided for operative movement transversely to the movement of the bolt and firing pin, means for causing operative movement of said member, and cooperating means carried by said member and by said bolt and said striker respectively for sequentially locking said bolt against retraction from its projected position and for projecting said striker into impacting engagement with the firing pin as an incident to operative movement of the said member.

4. The combination defined in claim 3, in which said cooperating means comprises cam means, including a cam surface on said member sloping relative to the operative movement of said member.

5. The combination defined in claim 4, in which said cam surface is disposed for sequential engagement with said bolt and with said striker respectively.

6. A firearm comprising a barrel formed with a bore therethrough defining a firing chamber at its rear end, and terminating rearwardly in a breech opening, a receiver operatively connected with said barrel, a bolt guided in the receiver for movement in a pre-determined path between rearwardly retracted and forwardly projected positions, selectively releasable means for retaining the bolt in its retracted position, and spring means for urging the bolt to its projected position, said bolt being formed with a passage therethrough in alignment with said barrel and said firing chamber and opening through the front and rear ends respectively of the bolt, and a firing pin slidably disposed in said passage for operative projection and retraction through the open forward end thereof, the improvement in accordance with which said bolt is formed with a forwardly-directed annular sealing surface within said passage, said firing pin being provided with a rearwardly-directed sealing surface in said passage for sealing engagement with the sealing surface of said bolt in the retracted position of the firing pin, a piston affixed to said firing pin rearwardly of the forward end thereof and within said passage, a portion of said passage snugly slidably receiving said piston and defining therewith a variable volume chamber forwardly of the piston, said chamber communicating with said breech opening through the open forward end of said passage, and firing pin actuating means for projecting said firing pin forwardly and im- 'mediately releasing same for rearward movement in response to the pressure of exploding gases in the firing chamber, the forward operating end of said firing pin being rigidly connected to said piston and projecting forwardly thereof, the diameter of said piston being substantially greater than the cross sectional dimension of the said operative end of the firing pin to expose a relatively-greater area of said piston to the gas pressure, said firing pin actuating means comprising a firing pin striker guided in said passage rearwardly of the firing pin for forward projection into impacting engagement with the firing pin, said striker being fully received in said passage at the time of such engagement, and means resiliently urging said firing pin striker rearwardly to a pre-determined retracted position in which its rear end projects rearwardly from said passage and beyond the rear end of said bolt, a bolt lock member guided for operative movement transversely to the movement of the bolt and firing pin, means for causing operative movement of said member, and cooperating means carried by said member and by said bolt and said striker respectively for sequentially locking said bolt against retraction from its projected position and for projecting said striker into impacting engagement with the firing pin as an incident to operative movement of the said member, a cam surface on said member sloping relative to the operative movement of said member and cam surfaces on said bolt and said striker disposed respectively for engagement with the cam surface of said member, said bolt cam surface having a gentler slope than said striker cam surface, so that recoil forces acting on the bolt will transmit a proportionately smaller retractive force to said member than would be the case if such force were transmitted through the striker cam surface. 7. The combination defined in claim 6, in which said striker is disengaged from the firing pin throughout the range of its operative engagement with the said member, and said interengaged sealing surfaces are positioned to prevent retraction of the firing pin into engagement with the striker as thus retracted, thus to prevent the transmission of recoil forces from the firing pin to said member.

References Cited UNITED STATES PATENTS 410,320 9/ 1889 Emmens 89-27 522,509 7/1894 C-anet 8927 908,294 12/1908 Marga 89-191 X 2,231,879 2/1941 Brightman. 3,204,530 9/1965 McGowan 89-183 3,225,657 12/ 1965 Kruzell 89-187 3,227,045 1/ 1966 Kruzell 89191 X BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner. S. C. BENTLEY, Assistant Examiner. 

1. A FIREARM COMPRISING A BARREL FORMED WITH A BORE THERETHROUGH DEFINGING A FIRING CHAMBER AT ITS REAR END, AND TERMINATING REARWARDLY IN A BREECH OPENING, A RECEIVER OPERATIVELY CONNECTED WITH SAID BARREL, A BOLT GUIDED IN THE RECEIVER FOR MOVEMENT IN A PRE-DETERMINED PATH BETWEEN REARWARDLY RETRACTED AND FORWARDLY PROJECTED POSITIONS, SELECTIVELY RELEASABLE MEANS FOR RETANING THE BOLT IN ITS RETRACTED POSITION, AND SPRING MEANS FOR URGING THE BOLT TO ITS PROJECTED POSITION, SAID BOLT BEING FORMED WITH A PASSAGE THERETHROUGH IN ALIGNMENT WITH SAID BARREL AND SAID FIRING CHAMBER AND OPENING THROUGH THE FRONT AND MEDIATELY RELEASING SAME FOR REARWARD MOVEMENT IN REREAR ENDS RESPECTIVELY OF THE BOLT, AND A FIRING PIN SLIDABLY DISPOSED IN SAID PASSAGE FOR OPERATIVELY PROJECTION AND RETRACTION THROUGH THE OPEN FORWARD END THEREOF, THE IMPROVEMENT IN ACCORDANCE WITH WHICH SAID BOLT IS FORMED WITH A FORWARDLY DIRECTED ANNULAR SEALING SURFACE WITHIN SAID PASSAGE, SAID FIRING PIN BEING PROVIDED WITH A REARWARDLY DIRECTED SEALING SURFACE IN SAID PASSAGE FOR SEALING ENGAGEMENT WITH THE SEALING SURFACE OF SAID BOLT IN THE RETRACTED POSITION OF THE FIRING PIN, A PISTON AFFIXED TO SAID FIRING PIN REARWARDLY OF THE FORWARD END THEREOF AND WITHIN SAID PASSAGE, A PORTION OF SAID PASSAGE SNUGLY SLIDABLY RECEIVING SAID PISTON AND DEFNING THEREWITH A VARIABLE VOLUME CHAMBER FORWARD OF THE PISTON, SAID CHAMBER COMMUNICATING WITH SAID BREECH OPENING THROUGH THE OPEN FORWARD END OF SAID PASSAGE, AND FIRING PIN ACTUATING MEANS FOR PROJECTING SAID FIRING PIN FORWARDLY AND IMSPONSE TO THE PRESSURE OF EXPLODING GASES IN THE FIRING CHAMBER. 